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Experimental Study of Multiple Droplet Evaporative Cooling. Final Report. September 1991-December 1992.


pdf icon Experimental Study of Multiple Droplet Evaporative Cooling. Final Report. September 1991-December 1992. (4815 K)
Dawson, H. F.; diMarzo, M.

NIST GCR 93-624; Report 92-1; 116 p. April 1993.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
Telephone: 1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB93-198463

Keywords:

cooling; drop sizes; droplets; evaporation; solid surfaces; water; thermal conductivity

Abstract:

Techniques of infrared thermography were used to conduct an experimental study of the evaporative cooling of a hot, low thermal conductivity, non-metallic surface heated by radiation and subject to a random array of impinging water droplets. A droplet generating and distributing apparatus and a data acquisition system employing digital image analysis devices were also developed and implemented. Real time infrared images of the heated surface were recorded and digitized using computer resident fram grabbing hardware and analyzed on a pizel bases, giving a high degree of thermal and spatial resolution. From these analyses, the instantaneous surface temperature distribution and transient surface temperature profile were obtained for a range of initial temperatures and impinging mass fluxes. The surface temperature was found to decay exponentially with time to a steady state value for the fluxes used. Three dimensional plots of the temperature distribution on the surface also showed the significant lowering of the average surface temperature, and provided a qualitative description of the cooling phenomena at various stages during the transient. Results obtained will be used in the future validation of a computer model of the phenomena.